I originally formatted that as a series of 8 comments, but having it as a discussion is probably better.

1/8
I'd really like a way to see what the new Leader/Ruler Traits do, other than having to actually start a new game.

Right now I'm starting a very fictional new game just to see what 3 Traits do, Avant-Garde which always makes Enlightened Rulers, Genetic Memory which always gives Leaders the Ancestral Knowledge Trait, and Natural Refiners which gives the Propulsion Expert Trait to all Admirals. Avant-Garde is particularly puzzling since its effect on Pops seems to me to be quite unattractive, certainly not worth 1 Trait pooint, so I'm expecting that the Ruler Trait is the sweet, sweet juice. Here goes...


Okay, it seens to have worked, with my Leaders getting all 3 Traits if applicable.

2/8
Enlightened on Ruler seems unattractive, +50% Faction Unity gain. However, combined with the effect of the Pop Trait, I can see how it makes sense and can have some use cases.

The effect of Ancestral Knowledge on the Ruler/Leaders seems interesting. It gives them a Trait that has the same effect as if their level was 2 higher. This means that it synergizes with other effects that boosts starting level from 1 to 3 such as some vanilla Civics or the version of Transcendent Learning from the Perked Up Perks mod. Genetic Memory is itself also interesting, although it conflicts heavily with Avant-Garde.

One effect of this I particularly like is the +2 to Archeology Skill, although of course it's just analogous to the Scientist being 2 levels higher. I can most definitely see myself playing an Ancestral Knowledge run wher I combined it with perked-up Transcendental Larning. Very nice!

Propulsion Expert +10% sublight speed.


3/8
I'll try 2 other Traits, Stalwart and Intrepid, see what they do...

Valiant gives -10% War Exhaustion on Ruler, and also during Defensive Wars gives +0.5 Inf/m and +25% ship build speed. From Stalwart.

Admirals get 2 Traits. Underdog gives +15% Force Disparity Bonus (from Intrepid). Palatin gives +15% Home Territory Fire Rate, and +20% Daily Hull and Armour regeneration from Stalwart.

Oligotrophs gives Reliable Governors, which is +5 Pop Growth Speed and +5% Food from Jobs.

Urban gives Efficient Governors, which is +10% TV.

Megalomaniac gives Skyborn Architech Rules, which is +1 Megastructure capacity and +33% build speed to Megastructures, Titans, Colussus and Juggernaut. Interestingly this gives no effects on Pops.

4/8
Let's try a few more:

Apex Predators gives Pertinacious to Rulers (-10% Happiness, +10% ship damage general, and +33% damage vs a lot of specials including End Game Crises but not Marauders), and Opportunistic to Admirals (+15% Evasion, and +33% damage vs Guardians (i.e. Leviathans), and AEs and some others, but again doesn't seem to include Marauders. Also doesn't include non-awakened Fallen Empires and has no overlap with the bonuses from Pertinaceous).

Gifted Pilots gives Carrier Commander to Admirals (+10% Strike Craft damage and PD damage - I don't think this applies to Flak but not sure9, and Battle Mounts to Generals (+10% Army Morale damage, +10% Collateral damage, +10% Army Health).

5/8
I'll do at least one more:

Analytical gives Arcanist to Rulers (+33% to monthly Dar Matter, Zro and Living Metal), Forecaster to Generals (+15% Army damage, -155 Collateral damage, +25% Army XP Gain), and Pioneer to Scientists (-33% Survey Speed but 25% Anom Discovery chance).

Illustrious gives Regal to Rulers (+20 Edicts Fun, -5% Edicts Upkeep).

Natural Translucers gives Computing Expert to Admirals (+10% weapons range and +2 Accuracy).

I want to try the two other Big Naturals too...

Theoretical gives Life Weaver to Rulers (+1 Trait Point whether you're biological or Lithoid), and Naturalist to Governors (+5% Habitability, -5% Pop Upkeep).

Flexible gives Polymath Rulers (+1 Research Alternative).

Inquisitive gives Pathfinder to Scientists (+25 Survey Speed, +5% Anom chance - I'm going to check if this can be taken along with Analytical... and you can).


6/8
Practical gives Life Crafter to Rulers (+1 Robot Trait point), and Machinist to Governors (+5% Robot output, -5% Robot Upkeep).

Humble gives Dilligent to Governors (+10% Unity from Jobs).

Natural Chemists gives Gunnery Experts to Admirals (+5% ship weapon damage).

I want to see if I can try the last few ones, see what they give:

Crafty gives Forge Master to Governors. -10% Metallurgust Upkeep, +5% Engineering.

Creative gives Patron of the Arts to Governors. +5% Unity from Jobs, +5% Amenities.

Allergic gives "additional Traits and bonuses to Leaders". Looking at the existing Ruler and Leaders, as well as the recruiting pools for Gov/Sci/mil, I can't see any additional Traits. Not sure about bonuses. I'll try letting the game just run for 2 years... Nope... I'm not seeing anything.

Prideful makes Arrogant Admirals (-15% Combat Disengage, +25% Emergency FTL cooldown), and Cavalier Generals (-20% Army Disengage).

7/8
Obstinate generates 1 of 8 bad Ruler Traits, based on Ethos. I can't be arsed to look into that, at least not now. I do remember trying Obstinate long ago, back when Devious ran this show, and it felt pretty bad. But then again, it's a -2 trait. It's gonna need to ♥♥♥♥, and the effect upon Pops is *very* minor.

Sluggish gives Inert to Admirals (-10% Evasion), and Fastidious to Scientists (-15% Survey speed, -33% Anom/Archeo speed).

Hedonistic sometimes, repeat sometimes, gives the Profligate Trait to Rulers. It's stated that this Trait is 4 times more likely to appear. This must be some legacy stuff back from when Devious had Leader Traits have a chance to appear as opposed to always appearing. Probably warrants some clean-up.

8/8
Profligate seems to exist in different versions. One I saw but didn't pause the game but it included -25% Happiness. Ouch! Another I did record gives -10% TV and -10% Happiness... Yeah okay, I saw the worse one gain, -25% Happiness, -25% TV, +15% Leader Upkeep. But most Ruler candidates (Oligarchy) don't have Profligate. So this sems quite RNg.

Okay, I think that's all the Xenology Pop Traits that give Ruler/Leader Traits, although I haven't checked if any additional Traits are enabled for Bio-Trophies, Lithoids, Hive Minds or Machine Empires.